Most of the raw feed materials used for the production of strategic titanium metals and pigment are imported to the U.S. This dependence on foreign countries for sources of titanium is undesirable. The U.S. does contain sources of domestic perovskite ores, but a simple and cheap method of recovering titanium from perovskite ore has not been available.
One prior art method of processing perovskite for the recovery of titanium is disclosed in an article by G. W. Elger, W. L. Hunter, and J. E. Manser, entitled "Preparation and Chlorination of Titanium Carbide from Domestic Titaniferous Ores", in "Report of Investigations 8497, Bureau of Mines, 1980, pp. 20. According to this method, perovskite is reacted with carbon at high temperatures in an electric furnace to produce titanium carbide. This titanium carbide is then chlorinated to produce titanium tetrachloride. Unfortunately, this method is energy intensive and the carbide formed has an extremely high melting point which creates physical handling problems in the furnace.
Another prior art method for recovering titanium is disclosed in an article by Y. G. Goroshchenko, V. I. Belokoskov, Y. A. Fromin, and M. I Andreeva, entitled "Laboratory Experiments on Processing of Perovskite by Fusion with Ammonium Sulfate and Sulfuric Acid", Sbornik Trudov Khim, Tekhnol; Mineral; Syrlya, Kolsk; Poluostrova 1959, No. 1, pp. 25-39. In this method, a sulfuric acid-ammonium sulfate fusion is followed by leaching and precipitation. Unfortunately, the process is reagent intensive, the fusion mass is thick and sticky, and the reaction time is several hours.
A third method of recovering titanium is disclosed in an article by Y. G. Goroshchenko, D. L. Motov, G. V. Trofimov, and V. I. Belokoskov, entitled "Continuous Process of Sulfuric Acid Decomposition of Titanium-Niobium Concentrates", Invest; Karelski Kolsk; Filail, Akad; Narik S.S.S.R. 1959, No. 4, pp. 135-141. In this method, a sulfuric acid digestion that contains some ammonium sulfate is utilized and this is followed by extraction. The titanium is eventually precipitated as a double salt of ammonia. This process is complicated and is reagent intensive in that all excess acid is converted to ammonium sulfate by reaction with ammonia.
Another method for recovering titanium from perovskite is disclosed in Canadian Pat. No. 1,052,581 (Kelly and Oughton) entitled "Treatment of Calcium Titanate". In this method, perovskite is treated by roasting at 1200.degree. C. in hydrogen sulfide gas. This is followed by leaching to remove calcium and iron sulfides which leaves the titanium as titanium oxide. The disadvantages of this process are the high temperature and the use of highly toxic gas.
Still another procedure for recovering titanium is disclosed in an article by B. Kestriken, N. Melentiv and V. A. Reynichenko, entitled "Autoclave Opening of Perovskite Concentrate", Miner; Syre, Vses; Nanch.-Issled, Inst., Miner; Syrga, No. 13, 1966, pp. 63-69. In this procedure, perovskite is leached with nitric acid in an autoclave. Unfortunately, this chemical is expensive and corrosive.
As indicated above, there is a need for a simple and inexpensive method of obtaining titanium from perovskite.